This invention relates to a lubrication system for an internal combustion engine that also provides a ready source of supply of lubricant to one or more associated gear devices.
Internal combustion engines can be used to drive gear devices either directly or indirectly. Examples of directly driven gear devices as used herein are transmissions or differentials used to convert rotary motion of the engine output to rotary motion of a drive wheel. Examples of indirectly driven gear devices as used herein are locomotive traction motor gear boxes for motorized wheel assemblies. For these gear devices, an internal combustion engine drives an electric generator that produces electricity used to power an electric motor that turns the gears to drive the wheels.
Currently the lubrication systems for such gear devices are independent of the engine lubrication system and are generally self-contained. One problem with these types of lubrication systems is that the temperature of the gear lubricant is not easily maintained within a desired temperature range. In contrast, the temperature of the lubricant in an internal combustion engine including particularly a large internal combustion engine is relatively well controlled either by the engine coolant system or by a separate coolant system.
It would be desirable to control the temperature of the gear device lubricant as well as the engine lubricant, since most lubricants are typically optimized to provide maximum performance in a particular temperature range. For example, if the lubricant temperature is too high, the lubricant (which is comprised of a base lubricant and additives), begins to degrade or the lubricant viscosity becomes too low to provide optimum protection. If the lubricant temperature is too low, the lubricant additives may not be xe2x80x9cactivatedxe2x80x9d, or lubricant viscosity may be too high to properly flow to the gear device surfaces requiring lubrication.
Some gear devices use ambient air coolers to limit maximum lubricant temperature whereas others use the engine coolant system to limit both the high and low temperatures of the gear device lubricant by either pumping the lubricant from the gear devices through a line that runs through the engine coolant, or by pumping the engine coolant through a line that runs through or adjacent to the gear devices. A major drawback to this type of lubricant temperature control is that if a coolant leak were to occur into the gear device lubricant, it could lead to catastrophic failure.
Another problem with current gear device lubrication systems is that gear device lubricant leaks are not uncommon and are usually difficult to detect and/or check due to their location. Because the lubricant sumps for gear devices are small in relation to the size of an engine lubricant sump, a gear device lubricant leak can quickly deplete the lubricant in the gear devices, leading to catastrophic failure of the gear devices.
Still another problem with current gear device lubrication systems is that current trends in the industry are to extend gear device lubricant changes as long as possible, generally much longer than the engine lubricant change interval, whereby the removal of either normal or abnormal wear debris from the gear device lubricant may not be frequent enough to maximize the life of the gear devices.
The present invention relates to a lubrication system that overcomes the problem of controlling the temperature of the gear device lubricant by circulating a single lubricant (that is formulated to lubricate both the internal combustion engine and the gear devices driven either directly or indirectly by the engine) between the engine and the gear devices driven thereby.
Because of lubricant chemistry, such a lubrication system may be most appropriate where the engine is a heavy-duty diesel engine. However, it will be appreciated that such a lubrication system can also be utilized with non-diesel internal combustion engines if desired. Moreover, the lubricant can be formulated for typical engine lubricant change intervals, or for an automated system for maintaining the quality and level of lubricant in the system by periodically removing a portion of the used lubricant for either consumption along with the fuel or later reprocessing and adding fresh lubricant to maintain the lubricant level in the engine in the manner disclosed, for example, in U.S. Pat. No. 5,964,318 assigned to the same assignee as the present invention, the entire disclosure of which is incorporated herein by reference.
Such a lubrication system also overcomes the problem of minor gear device lubricant leaks since the engine lubricant sump is of sufficient size and is monitored on a sufficiently regular basis to minimize the risk of catastrophic failure of either the gear device or engine due to lubricant leaks. Further, the engine lubricant filtration device provides for removal of the gear device wear debris. Moreover, with the more regular engine lubricant change interval, complete removal of wear debris will occur more often.
In accordance with one aspect of the invention, the lubrication system circulates a portion of the lubricant that is circulated through the engine to one or more gear devices driven thereby and returns any excess gear device lubricant to the engine.
In accordance with another aspect of the invention, the lubricant pump that is used to circulate the lubricant through the engine also supplies a portion of the engine lubricant to the gear device(s).
In accordance with another aspect of the invention, a valve regulates the flow of pressurized lubricant from the engine to the gear device(s).
In accordance with another aspect of the invention, a single heat exchanger maintains the temperature of the lubricant passing through the engine and through the gear device(s) within a predetermined temperature range.
In accordance with another aspect of the invention, the filter that is used to filter the lubricant being circulated through the engine also filters the lubricant being circulated through the gear device(s).
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but several of the various way in which the principles of the invention may be employed.